The identification of sample containers serves for clearly identifying the sample to be analyzed so that the analysis results can be clearly allocated to the sample and incorrect allocations are avoided, in particular when a plurality of similar sample containers are used. A plurality of methods of identifying samples are known, which are used in accordance with the application purpose of the sample container.
In the simplest case, the sample container is marked by hand, for instance by a felt pen (e.g. a waterproof pen). If analysis devices having a read unit for automatically reading sample identifications are used, the hand-written identification can generally not be automatically read by the read unit. A measuring protocol provided with an identification therefore usually requires the manual input of the identification into an input unit of the analysis device. This requires more work with the risk of incorrect allocation when the identification is incorrectly input.
A further possible allocation of the sample container may for instance be performed indirectly through a position number of the sample container in a magazine. This disadvantage is that a clear identification of the sample container is not detected automatically and therefore a manual allocation of the sample container and the position number is required. Incorrect allocations between the sample (sample container) and the position number may occur, in particular when a plurality of magazine charges are to be analyzed.
In analysis devices having a read unit for reading sample container identifications, as e.g. a bar code, a clear allocation of the sample container identification and the analysis results is performed as schematically shown in FIG. 1.
The sample container 1 is provided by the user with a machine-readable code 2, which is for instance printed onto an identification label. The identification may for instance be generated by means of a computer 3 by a printer (encoding means) 4 and may be adhered onto the sample container 1. The sample container 1 is identified (decoded) in the analysis device 5, wherein the identification along with the measuring results is handed back to the computer. As an alternative to the adhesive label, the identification can also be printed directly onto the sample container, wherein, however, each user requires a special identification unit (encoding means 4) instead of a conventional printer, which allows the marking of sample containers. An identification unit of that kind usually causes clearly higher costs of purchase and can be used for a specific purpose only. When using adhesive labels, disadvantages may result with respect to the constructional tolerances of the sample containers, since the adhesive label changes the dimensions of the sample container which is provided with a label. In the head space gas-chromatography, the sample container is heated up to a temperature of approximately 300° C., wherein the thermostatization of the sample container is performed in a small opening with very narrow tolerances within a heating block. Thus, an identification by adhesive labels cannot be performed. Furthermore, the adhesives of the adhesive labels have a temperature stability insufficient for this application. The attachment of the identification by hand is also often not practicable, since in case of precision measurements the sample containers should not be touched after a cleaning process in order to avoid impurification and therefore a falsification of the analysis results.
A further decisive disadvantage of the methods described so far is that constituents of the identification ink or constituents of the adhesive of the adhesive label or of the label contaminate the substance analyzed during measurement, in particular when the sample containers and samples are severely heated as in head space gas-chromatography (e.g. to 300° C.).